Communication devices such as User Equipments (UEs) are also known as e.g. mobile terminals, wireless terminals and/or mobile stations. A user equipment is enabled to communicate wirelessly in a cellular communications network, wireless communications system, or radio communications system, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
The user equipment may further be referred to as a mobile telephone, cellular telephone, laptop, Personal Digital Assistant (PDA), tablet computer, surf plate, just to mention some further examples. The user equipment in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the RAN, with another entity, such as another user equipment or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. By the base station serving a cell is meant that the radio coverage is provided such that one or many user equipments located in the geographical area where the radio coverage is provided may be served by the base station. One base station may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipment within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
In the context of this disclosure, the expression downlink (DL) is used for the transmission path from the base station to the user equipment. The expression uplink (UL) is used for the transmission path in the opposite direction i.e. from the user equipment to the base station.
In current cellular communications network there are situations when a cell is in outage. Such cell may be referred to as an outage cell. The outage cell is a cell normally able to serve one or more user equipments, but that is malfunctioning in this regard for some reason. The reason may e.g. hardware or software failure in a base station that normally serve the cell, but can also be that the cell deliberately has been put in a temporal inactive state, such as for repair or maintenance of the base station. By user equipment served in a cell is referred to, in a shorter and more convenient manner, that the user equipment is located in the geographical area where the radio coverage is provided by the base station serving the cell and that the user equipment is being served by the base station.
Hence, when a cell is in outage, no user equipment is able to be served in the cell and if there is no possibility to connect to another base station in the neighbourhood, a coverage hole is created in the cellular communications network. In addition to negative consequences for a user equipment that no longer can access services in the cellular communications network, the situation is also highly undesirable for an operator of the cellular communications network. For example, potential revenue is missed from loss of traffic in the outage cell. Also customer satisfaction may be damaged.
A common practice today is that the operator aims at restoring the original coverage by correcting the cell outage, but that no compensational measures are taken in the meantime.
WO2011/102767A1 discloses a method and a device for automated compensation for a cell/sector outage. Parameters of uplink power control are adjusted in order to trade-off coverage versus quality. The uplink power control parameters can be continuously optimized in response to traffic and network characteristics thereby providing for an optimized performance degradation in cells surrounding the coverage hole.
Nevertheless, it is still desirable with further improvements for compensating cell outage.